1. Field of the Invention
The present invention relates to a method of manufacturing book blocks from various printed sheets composed of a plurality of quarto sheets which are inserted into one another, wherein the printed sheets are successively pulled fold first along a conveying path from a stack of printed sheets by gripping means of a feeder and are subsequently gathered with their flat sides placed against each other into book blocks.
2. Description of the Related Art
The above-described method is used for preparing, inter alia, book blocks in a gathering machine for gluing. A gathering machine is disclosed, for example, in DE-C-31 26 769. This gathering machine is composed of several feeding stations arranged along a conveying device which individually grasps the printed sheets stacked in a magazine on the side of the fold by means of revolving gripping drums and places the printed sheets in motion. The printed sheets which reach the conveying device approximately at a right angle to the conveying flow direction of the conveying device are transported from feeding station to feeding station by drive members which revolve on a pulling means, wherein additional printed sheets continue to be supplied and placed until the desired book block is formed.
The processing of printed sheets which are formed of quarto sheets inserted into one another, i.e., formed with three open side edges and also called tabloids, is frequently difficult because of the change of direction of the movement of the sheets at the transfer point of the drive members of the conveying device. The abrupt change of direction of the printed sheets from a direction of movement perpendicularly to the fold into a movement parallel to the fold may cause the individual quarto sheets to be shifted relative to each other, particularly when they are of lightweight paper, wherein these shifts can no longer be corrected during the continuing treatment process. Particularly the quarto sheets of a printed sheet placed on top has the tendency to be lifted off because it rests only loosely on the top and may also be moved by the ambient air in the conveying direction relative to the other printed sheets.
These irregularities lead to waste and render the process unreliable.